Generally, the fundamental steps for processing color light-sensitive materials are a color development step and a desilvering step. Namely, an exposed silver halide color photographic material is processed in a color development step. In this step, silver halide is reduced by a color developing agent to form silver and, at the same time, the oxidized color developing agent reacts with color couplers to form dye images. Thereafter, the color photographic material is processed in a desilvering step. In this step, silver formed in the prior step is oxidized by the action of an oxidizing agent (which is generally called a bleaching agent) and thereafter it is removed by dissolving with a complexing agent for silver ions which is generally called a fixing agent. Consequently, only dye images are present in the photographic materials processed by these steps. Practical development processing includes auxiliary steps for keeping good photographic or physical quality of the images or for improving storage stability of the images in addition to the above described fundamental steps of color development and desilvering. For example, a hardening bath for preventing excessive softening of light-sensitive layers during processing, a stopping bath for effectively stopping the development reaction, an image stabilizing bath for stabilizing the images and a defilming bath for removing the backing layer on the support are known auxiliary steps.
Further, with respect to the above described desilvering step, two approaches exist, namely, the two steps wherein the bleaching bath and the fixing bath are separate from each other and one step wherein the bleach-fixing bath containing a bleaching agent and a fixing agent is used in order to further simplify the processing for the purpose of rapid treatment and reduction of labor.
Potassium ferricyanide and ferric chloride used hitherto as bleaching agents are excellent from the standpoint of the large oxidizing power they possess. However, since bleaching solutions or bleach-fixing solutions using potassium ferricyanide as a bleaching agent release cyanide by photolysis to cause disposal problems, waste liquors containing such should be processed in order to completely remove pollution problems. Further, bleaching solutions using ferric chloride as a bleaching agent have not only the disadvantage that they easily cause apparatus corrosion, because they have a very low pH and a very large oxidizing power, but also the disadvantage that iron hydroxide is precipitated in the emulsion layers in the water wash step after the bleach treatment is carried out with stains arising.
On the other hand, potassium bichromate, quinones and copper salts, etc., have been used hitherto as bleaching agents, but they have disadvantages that they have a low oxidizing power and they are difficult to handle.
In recent years, for rapid simple processing and prevention of environmental pollution, a bleach treatment using ferric ion complex salts (for example, ferric ion complex salts of aminopolycarboxylic acids, etc., and, particularly, ethylenediaminetetraacetato iron (III) complex salts) as main components is utilized for color photographic light-sensitive materials.
However, ferric ion complex salts have a comparatively low oxidizing power and an insufficient bleaching power. Therefore, although the desired object can be attained to some extent by using them in a bleach treatment or bleach-fixing treatment of low speed silver halide color photographic light-sensitive materials comprising silver bromochloride emulsions as the main components, disadvantageously the bleaching action is insufficient resulting in inferior desilvering or a long period of time is required for bleaching in processing spectrally sensitized high speed silver halide color photographic light-sensitive materials comprising silver chlorobromoiodide or silver iodobromide emulsions as the main components, particularly, color reversal light-sensitive materials for photography which contain high silver content emulsions and color negative light-sensitive materials for photography.
Persulfates are known as bleaching agents other than ferric ion complex salts. Persulfates are generally used in a bleaching solution containing chlorides. However, bleaching solutions using persulfates have the disadvantage that the bleaching power is inferior to that of ferric ion complex salts and a very long period of time is required for bleaching.
As described above, bleaching agents which do not cause pollution problems and do not corrode apparatus have an inferior bleaching power. Accordingly, it has been desired to increase the bleaching ability of the bleaching solutions or bleach-fixing solutions using bleaching agents having a poor bleaching power, particularly, ferric ion complex salts and persulfates.
Hitherto, additions of various bleaching accelerators to processing baths in order to increase bleaching ability of the bleaching solutions or bleach-fixing solutions containing a ferric ion complex salt such as iron salt of ethylenediaminetetraacetic acid as a bleaching agent have been proposed. Examples of such bleaching accelerators are, for example, the thiourea derivatives described in Japanese patent publication 8506/70 and U.S. Pat. No. 3,706,561, selenourea derivatives described in Japanese Patent Application (OPI) 280/71 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), 5-member ring mercapto compounds described in British Pat. No. 1,138,842, and thiourea derivatives, thiazole derivatives and thiadiazole derivatives described in Swiss Pat. No. 336,257, etc. However, many of these bleaching accelerators do not always show a satisfactory bleach acceleration effect or they have the disadvantage that the useful life of the processing solutions is short and the processing solutions cannot be stored for a long period of time, because they are not stable processing solutions.
Further, a method using 4-carboxythiazolidine derivatives as bleaching accelerators is described in Japanese Patent Publication No. 9854/78. However, these bleaching accelerators have the disadvantage that the useful life in the processing solutions is short, because they have a poor bleach accelerating effect and lack stability as a processing solution.